Gaskets General: Types of gaskets

Materials for gaskets can be divided into three main categories:

• Non-Metallic types

ASME B16.21 covers types, sizes, materials, dimensions, dimensional tolerances, and markings for non-metallic flat gaskets

250-500 AARH (3,2 – 12,5 µm), it is called stock finish and specified for soft gaskets such as NON Asbestos, Graphite sheets, Elastomers etc. If we use smooth finish for soft gaskets enough "biting effect" will not occur and hence the joint may develop leak.

• Semi-Metallic types

ASME B16.20 covers materials, dimensions, dimensional tolerances, and markings for metallic and semi-metallic gaskets.

125-250 AARH (3,2 – 6,3 µm), it is called smooth finish and specified for Spiral Wound Gaskets

• Metallic types

ASME B16.20 covers materials, dimensions, dimensional tolerances, and markings for metallic and semi-metallic gaskets

63 AARH is specified for Ring Type Joints. (1,6 µm),

Flexibiliteit van een pakking wordt vaak aangegeven met de compressie en de relaxatie van een pakkingmateriaal.

- Samendrukbaarheid volgens ASTM F36J: 10%

- Terugvering volgens ASTM F36J: 60%

Percentage compressie is op basis van de dikte van het materiaal (nieuwe pakking)

Terugvering is een percentage van de ingedrukte hoeveelheid.

AARH stands for Arithmetic Average Roughness Height. It is used to measure the roughness (rather smoothness) of surfaces. 125 AARH means 125 micro inches will be the average height of the ups and downs of the surface.

Sometimes AARH is referred also as Ra which stands for Roughness Average and
means the same.

µm The micrometer SI symbol: μm or micrometer (American spelling), also commonly known by the previous name micron, is an SI derived unit of length equaling 6994100000000000000♠1×10−6 metre (SI standard prefix "micro-" = 10−6); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm.

Example 6,3 µm = 0,0630 Millimeter